Impaired Design Fluency Is a Marker of Pathological Cognitive Aging; Results from the Korean Longitudinal Study on Health and Aging

OBJECTIVE We investigated neuropsychological markers that can be used to discriminate pathological cognitive aging from normal cognitive aging. METHODS We administered frontal lobe function tests including the Wisconsin Card Sorting Test (WCST), digit span test, lexical fluency test, fixed condition design fluency test, and Trail Making Test B (TMT-B) to 92 individuals with pathological cognitive aging (PCA) and 222 individuals with normal cognitive aging (NCA). We examined the main effects of participants' diagnoses (PCA, NCA) and age (65-69 years old, 70-74 years old and 75 years old or over) on their test performance using multivariate analysis of variance. RESULTS The main effects of both the diagnosis (F=2.860, p=0.002) and the age group (F=2.484, p<0.001) were significant. The PCA group showed lower performance on the backward digit span test (F=14.306, p<0.001), fixed condition design fluency test (F=8.347, p=0.004) and also exhibited perseverative errors in the WCST (F=4.19, p=0.042) compared with the NCA group. The main effect of the diagnosis on the backward digit span test and the fixed condition design fluency test remained significant after Bonferroni correction. The main effect of age remained significant in the TMT-B (F=8.737, p<0.001) after Bonferroni correction. Other test scores were not influenced by diagnosis or age. CONCLUSION The design fluency task may be a good neuropsychological marker to assess pathological cognitive aging.